If a written constitution is good enough for Europe, why not for Britain?

The proposal of the Foreign Secretary that the European Union should have a written constitution marks the final stage in a government rethink that has been more than a year in the making. Time was, shortly after the Treaty of Nice was concluded 18 months ago, when the Government that had promised to be "at the heart of Europe" would have run a mile rather than sign up to a written definition of rights and obligations within the EU. Such clarity, it felt, was not to be encouraged, lest the clarity be of an unwelcome sort.

Now, several months of cautious kite-flying has produced the new line: let Europe have a constitution, and let Britain take a leading role in its writing. In striking a tone that is more positive than the constant carping about EU bureaucracy, the change is decidedly for the better. But it also makes excellent sense.

One of the biggest deficiencies of the EU as it is currently constituted is the gap between its institutions and the people of Europe. There are real questions about the accountability of the European Commission and real questions, too, about the power, or lack of it, of the European Parliament. As Jack Straw said yesterday, Europe faces "something of a crisis of legitimacy". And he admitted: "Polls across Europe demonstrate lukewarm levels of support for the union."

A constitution, by itself, would not necessarily change that. What it could and should do, however, is set out in black and white the rights and obligations of member-countries. It should set out their judicial relationship, with each other and with the institutions of the European Union at the centre. In particular, it should spell out the much-quoted and variously interpreted principle of "subsidiarity".

The application of this principle – that decisions should be taken at the lowest level at which they can be effective, and that Europe's writ should run only where decisions need to be enacted Europe-wide – is at present uncertain and applied inconsistently. There are times when the sovereignty of democratically elected national governments comes close to being violated. There are times when European red tape ties up the implementation of decisions that would have been far better left to local authorities. "Subsidiarity" needs to be formally documented in a way that all countries, and EU bodies themselves, understand.

The key to an EU constitution is that it should be simply formulated and restricted to basic principles. It should, as Mr Straw said, "set out in plain language what the EU is for and how it can add value". As he says, too, it should also "reassure the public that national governments remain the primary source of political legitimacy".

A European constitution is no simple matter. It is worth having only if it functions as a guardian of Europe's democracy. It must be drafted in a way that allays fears that it could bring forth, or sanction, a super-state. And procedures for challenging decisions as "anti-constitutional" must be structured to discourage long-running and complex lawsuits. Rulings must be as simple as the rules.

In countering the howls of "super-state" from Eurosceptics, Mr Straw rightly said there was nothing inherently supra-national about a constitution: golf clubs had them, as did political parties – even the Tories. The flaw in his argument, however, is that his country, our country, does not. It may be that our democratic safeguards, worked out haphazardly over centuries, are as effective as any written constitution. But they may not be. If the Government is to advocate a constitution for Europe, it needs a good reason why British citizens should not have one, too.